There is different robust estimation methods
used for detecting small gross errors which may be presence
in geodetic observations. Some of these methods are
robust M-estimators, Least Absolute Sum and Danish
method. The conventional Least Squares Estimation
method and these robust estimation methods have been
tested and applied on a precise geodetic network designed
for detecting earth’s crustal deformations using singlepoint
and rigid body displacement models. The results
show that, the method of least squares leads to biased,
unfavorable solution and useless estimates if the singlepoint
displacement does not taken into considerations in
the solution’s mathematical model. In contrast, the results
of robust estimation methods are attained unbiased in a
single estimation step. A reliable separation of single-point
displacement and the general deformation model is
achieved without difficulties. The comparison of results
proved that, the Danish method gave the most accurate
results. It also was more sensitive to outliers which may be
presence in surveying observations in case of applying
single-point displacement model. The Least Absolute Sum
method was very nicely reproduces the simulated deformations
and does not show a contamination of the estimated
positions of stable points in the case of rigid body
displacement model. The results of adjustment using rigid
body displacement model were not identical with the
nearly correct results of single-point displacement model.
So, the rigid body displacement model may be not suitable
for geodetic networks. |
